RPE/choroidal whole mounts were prepared as described previously.[43 (link)] Briefly, tissues were permeabilised with 0.3% triton X-100 for 1h. The samples were then blocked with 6% BSA and incubated with biotinylated Griffonia Simplicifolia Lectin I-Isolectin B4 (1:100, Vector Laboratories Ltd, Peterborough, UK) and rabbit anti-mouse collagen IV (1:100, ABD Serotec Ltd, Oxford, UK), followed by FITC-conjugated Streptavidin (1:200, Dako, Denmark) and goat anti-rabbit AlexFluor 594 (1:200, Invitrogen, Paisley, UK) for 2h. Samples were observed by confocal microscopy (Eclipse TE200-U, Nikon UK Ltd, Surry, UK).